This invention relates to electric motors, and more specifically to the control of electric motors.
Electric motors are used for numerous applications wherein daytime and nighttime operations differ. For example, fractional horsepower AC electric motors used as swimming pool pump motors are operated at a high speed during the day, when swimming pool usage and sunlight's effect on algae formation demand maximum circulation and filtration; at night, the motors are typically shut off or run at lower speed because the pool is unused or used minimally, and algae growth is minimal due to the absence of sunlight. Two-speed pump motors, for example, typically run at half speed at night to provide additional filtration at approximately one-fifth the electrical consumption.
Conventionally, manually set timers have been utilized to automatically turn such pump motors on at a pre-set time early in the day, and to disable or slow the motor at a pre-set time at the end of the day. Those skilled in the art, however, recognize that the timer mechanism is separately mounted to a wall or fixture, and that it must be wired to the motor. That additional mounting and wiring typically requires installation by a skilled person, and adds to the cost. Moreover, seasonal changes in the hours of daylight require the timer to be periodically reset by the user.